1. Field of the Invention
The present invention relates to a gas turbine, and especially, relates to a gas turbine which is expected to put such control technology into practical use as controls the temperature, pressure and flow volume of a cooling fluid for blade rings and segment rings in order to cool stationary vanes and rotating blades and of a cooling fluid for a rotor.
2. Description of the Prior Art
Generally, a gas turbine mainly consists of three elements including an air compression part (“compressor” hereinafter), a combustion part (“combustor” hereinafter) and a turbine part; wherein a combustor is installed between the compressor and the turbine part that are directly connected to each other by a main shaft. Here, FIG. 8 shows a longitudinal cross-sectional view of a turbine part of a general gas turbine.
As shown in FIG. 8, a turbine part has a main shaft installed inside a casing 1 constructing an outer shape thereof so as to be able to rotate; wherein, the main shaft has the rotor discs 2A, 2B, 2C and 2D provided axially thereto in a plurality number of stages, for example, in four stages; and a plurality of rotating blades 3A, 3B, 3C and 3D extend in a radial pattern from the outer circumference of each of the rotor discs 2A, 2B, 2C and 2D. The rotor discs 2A, 2B, 2C and 2D and the rotating blades 3A, 3B, 3C and 3D comprise each of the rotating blade rotors 4A, 4B, 4C and 4D, rotating together with the main shaft in an integrated manner.
Additionally, inside the casing 1, the stationary vanes 5A, 5B, 5C and 5D are installed in a manner that they are arranged, alternating with the rotating blades 3A, 3B, 3C and 3D in each stage along the main shaft. The stationary vanes 5A, 5B, 5C and 5D in each stage are installed to the shrouds 6A, 6B, 6C and 6D on the side of the outer circumference, surrounding each of the stationary vanes 5A, 5B, 5C and 5D in each stage concentrically against the main shaft.
In addition, inside the casing 1, the blade rings 7A, 7B, 7C and 7D are coupled, surrounding each of the stationary vanes 5A, 5B, 5C and 5D and the rotating blades 3A, 3B, 3C and 3D in each stage concentrically against the main shaft. Inside the blade rings 7A, 7B, 7C and 7D in each stage, is coupled respectively each of the outer-circumference-side shrouds 6A, 6B, 6C and 6D, having the stationary vanes 5A, 5B, 5C and 5D installed thereto; and at the same time, ring segments 8A, 8B, 8C and 8D are coupled, surrounding each of the rotating blades 3A, 3B, 3C and 3D respectively in a concentric manner against the main shaft.
In a turbine part of a gas turbine as described hereinabove, high temperature and high pressure combustion gas is fed from a transition piece of a combustor through a gas path 9, serving as a working fluid; wherein by having the combustion gas flow to the stationary vanes 5A, 5B, 5C and 5D and the rotating blades 3A, 3B, 3C and 3D in each stage alternatively in sequence from the first stage through the fourth stage, the main shaft is rotary driven with the rotating blades 3A, 3B, 3C and 3D, namely the rotating blade rotors 4A, 4B, 4C and 4D. Then, when a generator is connected to a front edge of the main shaft, turning force of the main shaft is utilized as a source of electric power generation. On the contrary, when an injection port is installed to an end of the turbine part for exhaust of combustion gas, turning force of the main shaft is utilized as a jet engine.
In addition, in a compressor of a gas turbine, a rotating blade rotor rotates by rotation of the main shaft in the same manner as the turbine part, thereby inhaling the air in from the outside to be served as a working fluid; and the air is transported to a combustor, being compressed, going through the rotating blades and the stationary vanes alternatively. Compression air being introduced to the combustor burns herein together with a fuel being supplied, resulting in high temperature and high pressure combustion gas, which will be sent to the aforementioned turbine part.
Meanwhile, because high temperature combustion gas flows in the turbine part of a gas turbine, serving as a working fluid, cooling construction is indispensable in order to prevent excessive increase in temperature of the stationary vanes 5A, 5B, 5C and 5D and the rotating blades 3A, 3B, 3C and 3D. Generally, in order to cool the stationary vanes 5A, 5B, 5C and 5D, cooling fluid such as high pressure air and/or steam is introduced to each of the spaces 10A, 10B, 10C and 10D that are formed by the blade rings 7A, 7B, 7C and 7D in each stage and the casing 1, thereby cooling the blade rings 7A, 7B, 7C and 7D and the shrouds 6A, 6B, 6C and 6D on the outer circumference side, through which the cooling fluid for the blade rings is introduced to the stationary vanes 5A, 5B, 5C and 5D so as to cool them. The cooling fluid for the blade rings is also used for cooling the ring segments 8A, 8B, 8C and 8D, which will be referred as “cooling fluid for blade rings/ring segments” hereinafter. On the other hand, in order to cool the rotating blades 3A, 3B, 3C and 3D, cooling fluid such as high pressure air and/or steam is introduced into the inside of the rotor discs 2A, 2B, 2C and 2D in each stage, thereby cooling the rotor discs 2A, 2B, 2C and 2D, which makes the cooling fluid for rotors introduced to the rotating blades 3A, 3B, 3C and 3D to cool them.
Moreover, in recent years, as for the above-mentioned cooling fluid for blade rings/ring segments and the cooling fluid for rotors, it is examined to put a technology controlling the temperature, the pressure and the flow volume thereof into practical use in accordance with the operation condition. (For example, see the Japanese Patent Application Laid-Open No. 2001-248406.) This technology aims at mitigating the fluctuation of thermal expansion and contraction of the rotating blades 3A, 3B, 3C and 3D against the ring segments 8A, 8B, 8C and 8D during operation of a gas turbine (especially, during start-up), and constantly controls so as to secure a moderate amount of minute clearance between the tips of the rotating blades 3A, 3B, 3C and 3D, serving as the edges of the outer circumferences thereof, and the inner circumference surfaces of the ring segments 8A, 8B, 8C and 8D without contacting each other, thereby trying to improve performance of the gas turbine further.
In order to realize the above, sensors are installed in order to detect the clearance between the tip of the rotating blade 3A or 3B in the first or the second stage, which is especially subject to strong thermal impacts due to being exposed to high temperature combustion gas, and the inner circumference surface of the ring segment 8A or 8B, monitoring the aforementioned clearance. Based on the output of the sensor, the temperature, the pressure and the flow volume of the cooling fluid for blade rings/ring segments and the cooling fluid for rotors are adjusted so as to obtain a moderate amount of minute clearance between the tip of the rotating blade 3A or 3B and the inner circumference surface of the ring segment 8A or 8B in the first or the second stage, and as a result, the fluctuation of thermal expansion and contraction of the rotating blades 3A, 3B, 3C and 3D against the ring segments 8A, 8B, 8C ad 8D in each stage can be minimized.
Here, FIG. 9 shows a conventional structure of installation of a sensor. In this figure, installation structure of a sensor is shown, which is employed for detecting a clearance between the tip of the rotating blade 3B and the inner circumference surface of the ring segment 8B in the second stage. As shown in FIG. 9, the sensor 120 is a FM modulation capacitance type sensor, mainly consisting of an anterior portion 121 which houses a detecting element having a detection zone forward, a posterior portion 122 which leads a cable 130 transmitting outputs from the detecting element backward, and a collar portion 123 which connects both anterior and posterior portions. The cable 130 whose copper wire serving as a signal line is clad with an insulating material is led out from the sensor 120 through a leading-out outlet 124 being formed in the posterior portion 122.
The sensor 120 as described hereinabove has the posterior portion 122 thereof inserted into the edge of a first guide pipe 140 made of metal such as stainless and the like; wherein, the edge of the first guide pipe 140 and the corner portions of the rear surface of the collar portion 123 are connected by welding (See the symbol “W1” in FIG. 9.), thereby having the sensor 120 unified with the first guide pipe 140. The first guide pipe 140 integrating the sensor 120 penetrates through the casing 1 and the blade ring 7B from the outside of the casing 1 (being located upward in FIG. 9). Then, by being pressed forcedly toward the ring segment 8B by a compression coil spring (not illustrated) which is installed to the edge portion of the first guide pipe 140 on the side of the casing 1, the front surface of the collar portion 123 is pressed toward the pedestal 135 being fixed onto the outer circumference surface of the ring segment 8B so as to be held. The anterior portion 121 is inserted and penetrates through the through-hole 136 going through the pedestal 135 and the ring segment 8B, and consequently, the front surface of the anterior portion 121 comes to the top of the inner circumference surface of the ring segment 8B. Additionally, the cable 130 from the leading-out outlet 124 in the posterior portion 122 is introduced to the outside of the casing 1 through the first guide pipe 140 after being led to the inside of the first guide pipe 140.
Inside the first guide pipe 140, is introduced a cooling fluid such as high pressure air and/or steam from the edge on the side of the casing 1. This cooling fluid is supplied by a pump for exclusive use which is separately installed to the outside of the casing 1. The cooling fluid being introduced into the inside of the first guide pipe 140 cools the cable 130 itself and at the same time, cools the anterior portion 121 itself by being introduced to the periphery of the anterior portion 121 by way of the through-hole 125 which penetrates through the collar portion 123 of the sensor 120.
In addition, by having the first guide pipe 140 pressed forcedly by a compression coil spring, the sensor 120 is pressed toward the ring segment 8B. This is for the purpose of tolerating thermal expansion and contraction when the casing 1, the blade ring 7B, the ring segment 8B and eventually the first guide pipe 140 itself thermally expand and/or contract in accordance with a change in temperature during operation of a gas turbine.
However, it was discovered that in the conventional construction of installation of a sensor as described above, the following issues would occur due to being subject to vibrations during operation of a gas turbine. First, the cable 130 spins significantly at a high speed inside the first guide pipe 140, thereby making the cable 130 come in contact with the pipe wall of the first guide pipe 140 repeatedly, which abrades away the insulation cladding material thereof and consequently generates noises to the output signals transmitted by the cable 130.
Secondly, because the leading-out outlet 124 in the posterior portion 122 of the sensor 120 from which the cable 130 is led out is angular, the cable 130 comes in contact with the angular corner portions of the leading-out outlet 124 repeatedly due to rapid spinning at a high speed of the cable 130 inside the first guide pipe 140, which causes disconnection of the cable 130 in the contact portions.
Thirdly, although structurally, the sensor 120 can be pulled out and inserted from the outside of the casing 1 together with the first guide pipe 140, the welded joint portion W1 of the first guide pipe 140 to the sensor 120 fractures due to fatigue, which virtually results in separation, thereby causing a situation in which it is impossible to pull out or insert the sensor 120 together with the first guide pipe 140. This situation forces to stop operation of the gas turbine for a long period and then disassemble the casing 1 and the blade ring 7B in order to replace the sensor 120. Therefore, especially the third issue is directly related to the shutdown period of a gas turbine, so that consequently it will become a big obstruction to put the above-mentioned technology of controlling the temperature, the pressure and the flow volume of the cooling fluid for blade rings/ring segments and the cooling fluid for rotors into practical use.
In addition, as another example of construction of installation of a sensor as shown in FIG. 10, the first guide pipe 140 and the sensor 120 are completely separated as different members, wherein the sensor 120 is fixed to the ring segment 8B by sandwiching the front and rear surfaces of the collar portion 123 of the sensor 120 between a pedestal 135 and a holder 137 and joining the pedestal 135 and the holder 137 with a screw 138. In this case, the first guide pipe 140 being inserted from the outside of the casing 1 is retained by having the edge thereof on the side of the sensor 120 pressed onto the holder 137, receiving a pressing force of the compression coil spring. The cable 130 is guided along the inside of the first guide pipe 140 in the same manner as the construction of installation of a sensor shown in FIG. 9.
The construction of installation of a sensor as described hereinabove still generates the above-mentioned first and the second issues. In addition, because the sensor 120 is fixed to the ring segment 8B with a screw, it is impossible to replace the sensor 120 without disassembling the casing 1 and the blade ring 7B, so that the third issue still remains, too.
Moreover, as another example of construction of installation of a sensor as shown in FIG. 11, the first guide pipe 140 and the sensor 120 are completely separated as different members in the same manner as the construction of installation of a sensor in FIG. 10; wherein the sensor 120 is fixed to the ring segment 8B by sandwiching the front and rear surfaces of the collar portion 123 of the sensor 120 between the pedestal 135 and the holder 137 and joining the pedestal 135 and the holder 137 by welding (See the symbol W2 in FIG. 11.) In this case, the first guide pipe 140 being inserted from the outside of the casing 1 is retained by having the edge thereof on the side of the sensor 120 pressed onto the holder 137, receiving a pressing force of the compression coil spring, too. However, in this case, inside the first guide pipe 140 is provided a second guide pipe 150 which extends along the inside thereof, and the cable 130 is guided along the inside of the second guide pipe 150. The second guide pipe 150 is supported to the pipe wall of the first guide pipe 140 by a plurality of support plates 155 which extend along the second guide pipe 150.
In the construction of installation of a sensor as described hereinabove, because the cable 130 is inside the second guide pipe 150, rapid spinning at a high speed of the cable 130 is restrained, so as to be able to prevent the cable 130 from coming in contact with the first guide pipe 140. However, because the opening edge 151 on the side of the sensor 120 of the second guide pipe 150 is angular, the cable 130 comes in contact with this angular corner portions repeatedly so as to wear away. Therefore, the above-mentioned first issue still remains. In addition, although a significant spinning at a high speed of the cable 130 can be restrained, the leading-out outlet 124 of the posterior portion 122 of the sensor 120 remains to be angular, the above-mentioned second issue will still occur. Additionally, because the sensor 120 is fixed to the ring segment 8B by welding, it is impossible to replace the sensor 120 without disassembling the casing 1 and the blade ring 7B, so that the third issue still remains, too.